Semiconductor device and method of manufacturing same

ABSTRACT

A semiconductor device having a first semiconductor element placed over a second semiconductor element, so that an edge of the first semiconductor element is not placed over a predetermined circuit in the second semiconductor element, and wherein a size of the first semiconductor element is smaller than a size of the second semiconductor element. The predetermined circuit has a characteristic that tends to change with stress greater than characteristics of other circuits on the second semiconductor element that are under the edge of the first semiconductor element.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of application Ser. No. 10/893,257,filed Jul. 19, 2004, now U.S. Pat. No. 6,905,913 which is a divisionalapplication of application Ser. No. 10/401,763, filed Mar. 31, 2003, nowU.S. Pat. No. 6,777,801, which is a continuation application of Ser. No.09/685,590 filed Oct. 11, 2000, now U.S. Pat. No. 6,580,164, which arehereby incorporated by reference in their entirety for all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device wherein aplurality of semiconductor elements are sealed with a resin.

2. Description of the Related Art

In general, one has heretofore been known as a semiconductor device,wherein a semiconductor element or chip (hereinafter called “LSI chip”)incorporating therein Large Scale Integration (hereinafter called “LSI”)in which a plurality of circuits are integrated, is sealed with a resin.

FIG. 16 is a cross-sectional view showing an internal structure of aconventional semiconductor device 1. As shown in FIG. 16, an LSI chip 3is fixedly placed over a die 8 with an adhesive. A plurality of padelectrodes 5 placed over a main surface of the LSI chip 3 areelectrically connected to their corresponding leads 9 each of whichserves as a terminal for connection to the outside and is composed of aconductive material, by wires 7 used as metal thin lines or wires. TheLSI chip, 3, the pad electrodes 5, the die 8, the wires 7 and parts(corresponding to portions called “inner leads”) of the leads 9, whichinclude portions connected to the wires 7 respectively, are sealedwith-an insulating resin 10. The semiconductor device 1 is electricallyconnected to another device by parts (corresponding to portions called“outer leads”) of the leads 9 having led out of the resin 10, e.g., witha printed wiring board interposed therebetween, whereby the transfer ofsignals therebetween and the like are carried out.

When the LSI chip 3 is a system LSI for implementing combined functionsof a core of a central processing unit (hereinafter called “CPU”), amemory, other circuits used for peripheral functions, etc. as in thecase of, for example, a microcomputer (hereinafter called “micon”) orthe like, these functions are placed over the same semiconductorsubstrate in mixed form. Therefore, when the system LSI is equipped witha DRAM (Dynamic Random Access Memory) or a batch erasable EEPROM(Electrically Erasable Programmable Read Only Memory), a peculiarmanufacturing process is required which is not included in amanufacturing process (hereinafter called “Logic process”) forimplementing the CPU core and the circuits for the peripheral functions.As a result, a manufacturing process (corresponding to a process formixing of Logic and memory) peculiar to the system LSI is appliedthereto to develop products with a view toward implementing such asystem LSI.

A semiconductor device in which a plurality of LSI chips are sealed witha resin to bring it to the commercial stage (i.e., a plurality ofsemiconductor elements are stored or held in one package), has appearedin recent years. Such a semiconductor device is referred to as “MCP(Multiple Chip Package) type”. The semiconductor device of the MCP typeis applied to a memory-system LSI. The semiconductor device is appliedto, for example, a case in which memories identical in type are held oraccommodated in one package to implement an increase in memory capacity,or a case in which memories of types different in function from oneanother are held in one package to thereby implement space saving.

FIG. 17 is a cross-sectional view showing an internal structure of anMCP type semiconductor device 11. FIG. 18 is a plan view illustratingthe internal structure of the MCP type semiconductor device 11. In FIGS.17 and 18, elements of structure structurally similar to those shown inFIG. 16 are identified by the same reference numerals.

As shown in FIGS. 17 and 18, an LSI chip 3 fixedly disposed with anadhesive is placed on a die 8. A plurality of pad electrodes 5respectively electrically connected to leads 9 by wires 7 are placedover a main surface of the LSI chip 3. Further, an LSI chip 13 isfixedly placed over the main surface of the LSI chip 3 with aninsulative adhesive interposed therebetween. A plurality of padelectrodes 15 are disposed over a main surface of the LSI chip 13. Thesepad electrodes 15 are electrically connected to their corresponding onesof the leads 9 by wires 17. These two LSI chips 3 and 13, parts of theleads 9, which include portions where they are respectively connected tothe wires 7 and 17, and the die 8 are sealed with a resin 10.

Thus, the MCP type semiconductor device 11 is configured so as toaccommodate or hold a plurality of the LSI chips 3 and 13 in one packageand have the leads 9 for connection to the outsides of the LSI chips 3and 13.

As such an MCP-compatible semiconductor device 11, there is known onelike BGA (Ball Grid Array), for example. This has such a structure thatdifferent types of memories such as a SRAM (Static Random AccessMemory), a batch erasable EEPROM, etc. are held or stored in onepackage, and input/output terminals of the memories are respectivelyindividually connected to the leads 9 to independently activate thememories respectively. Owing to such a structure, the functionscorresponding to the two LSI chips can be implemented by a space for oneLSI chip.

Thus, in the LSI, particularly, the system LSI built in thesemiconductor device, a mixed process is applied thereto to developproducts. In the memory-system LSI, the MCP type semiconductor device isapplied to implement an increase in memory capacity and bring differentmemories into combined form, thereby developing each product.

However, the semiconductor device equipped with the system LSI has thefollowing problems in that it is manufactured over the samesemiconductor substrate according to a specific process obtained byintegrating a manufacturing process peculiar to each memory into a Logicprocess.

A first problem is that since the number of masks increases comparedwith a Logic-single manufacturing process or a memory-singlemanufacturing process, a reduction in yield occurs. A second problem isthat the specific process no allows the facilitation of an improvementin the performance of a circuit for a Logic unit and an improvement inthe performance of a memory unit. A third problem is that since themanufacturing process becomes complex, TAT becomes long. A fourthproblem is that since the manufacturing process is complicated and thenumber of masks increases, process costs are raised. A fifth problem isthat the development itself of a process used for LSI obtained by mixingan LSI comprising an SOI (Silicon On Insulator) process which purses alow voltage/low current operation and an LSI comprising a specialprocess for fabricating high-withstand elementary devices(high-withstand MOS transistors, etc.) together is so difficult from atechnical viewpoint.

In an LSI to which a finer deep sub-micron manufacturing process isapplied, a reduction in voltage (about 0.8V to 1.5V) is accelerated evenin a Logic process from now on in particular. Thus, a plurality ofvoltages including a high voltage (e.g., 8V to 12V) higher than a sourcevoltage (e.g., 3.3V or 5V) are required upon rewriting and reading ofdata as in the case of the batch erasable EEPROM. It is thereforedifficult to implement a system LSI (such as a batch erasablememory-equipped micon or the like) configured by integrating ahigh-withstand process for building high-withstand elementary devicestherein and the Logic process therein.

Since the MCP type semiconductor device aims. to increase the capacityof each memory and provide space saving as described above, limitationsare imposed on the provision of leads for each individual LSIs toaccommodate or hold the same types of memory system LSIs in one packageor hold different types of memory system LSIs in one package andindependently operate the different types of memory system LSIsrespectively. Therefore, nothing was found to implement the system LSIfor the MCP type semiconductor device.

The present invention aims to solve the above problems and make itpossible to easily implement a system LSI by a semiconductor devicewherein a plurality of LSI chips are sealed with a resin.

Further, the present invention aims to solve problems developed uponimplementation of a system LSI by a semiconductor device wherein aplurality of LSI chips are sealed with a resin, and implement the systemLSI without impairing a function defined as for the system LSI ascompared with the prior art.

SUMMARY OF THE INVENTION

The present invention has been made to solve the foregoing problems andprovides, as a means, a semiconductor. device wherein a firstsemiconductor element and a second semiconductor element are sealed witha resin, comprising a plurality of first pad electrodes which are placedover a main surface of the first semiconductor element and which arerespectively electrically connected to any of a plurality of circuitsprovided over the first semiconductor element and electrically connectedto their corresponding plural terminals used for connection to theoutside, a plurality of second pad electrodes placed over the mainsurface of the first semiconductor element and respectively electricallyconnected to any of the plural circuits provided over the firstsemiconductor element, and a plurality of third pad electrodes which areplaced over a main surface of the second semiconductor element and whichare respectively electrically connected to circuits provided over thesecond semiconductor element and electrically connected to theircorresponding second pad electrodes, and wherein the first semiconductorelement executes a predetermined function by using the circuits providedover the second semiconductor element.

In the semiconductor device of the present invention owing to such aconfiguration, the second pad electrodes and the third pad electrodesare electrically connected to one another to allow the transfer ofsignals between the circuits provided over the first semiconductorelement and the circuits provided over the second semiconductor element.These two semiconductor elements are capable of implementing onefunction provided as for a system LSI. Therefore, the firstsemiconductor element and the second semiconductor element can bemanufactured individually, thus making it possible to solve the aboveproblems.

In the present invention as well, contrivances such as the placement orlayout of the second pad electrodes, the supply of a source voltage or aground voltage employed in the second semiconductor element, theplacement of means for selecting whether the circuits provided withinthe second semiconductor element should be used, etc. make it possibleto solve even problems developed upon implementation of a system LSI byan MCP type semiconductor device.

Typical ones of various inventions of the present application have beenshown in brief. However, the various inventions of the presentapplication and specific configurations of these inventions will beunderstood from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which is regarded as theinvention, it is believed that the invention, the objects and featuresof the invention and further objects, features and advantages thereofwill be better understood from the following description taken inconnection with the accompanying drawings in which:

FIG. 1 is a cross-sectional view showing an internal structure of an MCPtype semiconductor device 100 according to a first embodiment of thepresent invention;

FIG. 2 is a plan view illustrating the internal structure of the MCPtype semiconductor device 100 according to the first embodiment of thepresent invention;

FIG. 3 is a perspective view for describing the assembly of thesemiconductor device 100 shown in FIG. 1;

FIG. 4 is a block diagram showing a configuration of a micon 50 equippedwith a batch erasable EEPROM;

FIG. 5 is a plan view illustrating an internal structure of an MCP typesemiconductor device according to a second embodiment of the presentinvention, and is a view of the semiconductor device used as an EEPROMversion micon;

FIG. 6 is a plan view depicting the internal structure of the MCP typesemiconductor device according to the second embodiment of the presentinvention and is a view of the semiconductor device used as a mask ROMversion micon;

FIG. 7 is a diagram showing a circuit of an LSI chip 203 connected to apad electrode 205 a;

FIG. 8 is a conceptional diagram of a selector circuit 260 to which aselect signal SEL is inputted;

FIG. 9 is a specific circuit diagram of the selector circuit 260;

FIG. 10 is a plan view of a semiconductor device illustrative of amodification of FIG. 2;

FIG. 11 is a plan view of a semiconductor device illustrative of anothermodification of FIG. 2;

FIG. 12 is a plan view of a semiconductor device showing an applicationof FIG. 11;

FIG. 13 is a plan view of a semiconductor device showing a modificationof FIG. 12;

FIG. 14 is a plan view of a semiconductor device depicting anapplication of FIG. 13;

FIG. 15 is a plan view of a semiconductor device showing a modificationassociated with wire boding;

FIG. 16 is a cross-sectional view showing a conventional semiconductordevice;

FIG. 17 is a cross-sectional view illustrating another conventionalsemiconductor device;

FIG. 18 is a plan view depicting the semiconductor device shown in FIG.17;

FIG. 19 is a diagram showing a modification of a circuit for an LSI chip203, which is connected to a pad electrode 205 a;

FIG. 20 is a plan view illustrating an internal structure of an MCP typesemiconductor device illustrative of a modification of the secondembodiment of the present invention;

FIG. 21 is a diagram depicting a circuit for an LSI chip 203 connectedto a pad electrode 205 a and a pad electrode 205 b;

FIG. 22 is a diagram showing the layout of pad electrodes and leadsemployed in the modification of the present invention;

FIG. 23 is a diagram illustrating another example of a circuit for anLSI chip 203 connected to a pad electrode 205 a and a pad electrode 205b;

FIG. 24 is a diagram showing the layout of internal circuits where abatch erasable EEPROM is used as an LSI chip 913 corresponding to theLSI chip 203;

FIG. 25 is a plan view depicting an LSI chip 903 stacked on a mainsurface of the LSI chip 913;

FIG. 26 is a plan view illustrating the relationship of placementbetween the LSI chip 903 and the internal circuits in the LSI chip 913both shown in FIG. 25;

FIG. 27 is a cross-sectional view of a semiconductor device wherein thetwo stacked LSI chips shown in FIG. 25 are resin-encapsulated;

FIG. 28 is a view showing a modification of the layout of the internalcircuits in the LSI chip 913;

FIG. 29 is a plan view illustrating an LSI chip 903 layered over themain surface of the LSI chip 913 in the modification shown in FIG. 28;

FIG. 30 is a cross-sectional view (corresponding to a cross-sectionalview taken along line A-A′) depicting a semiconductor device wherein thetwo layered LSI chips shown in FIG. 29 are resin-encapsulated; and

FIG. 31 is a cross-sectional view (corresponding to a cross-sectionalview taken along line B-B′) showing a semiconductor device wherein thetwo stacked LSI chips shown in FIG. 29 are resin-encapsulated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Semiconductor devices of the present invention will hereinafter bedescribed in detail with reference to the accompanying drawings. FIG. 1is a cross-sectional view showing an internal structure of an MCP typesemiconductor device 100 according to a first embodiment of the presentinvention, and FIG. 2 is a plan view illustrating the internal structureof the semiconductor device 100, respectively. In FIG. 1, the sameelements of structure as those shown in FIGS. 16 through 18 areidentified by the same reference numerals.

In FIGS. 1 and 2, the semiconductor device 100 has an LSI chip 103 whichserves as a first semiconductor element, and an LSI chip 113 whichserves as a second semiconductor element. The LSI chip 103 and the LSIchip 113 are both similar in shape to each other (rectangular in thepresent invention).

The LSI chip 103 is fixed and placed on a substantially central area ofa die 8 with an adhesive provided between the reverse side or back ofthe LSI chip 103 and the die 8. A plurality of first pad electrodes 105are placed over a main surface of the LSI chip 103. In the firstembodiment, the respective pad electrodes 105 are respectively placed inline along the two parallel sides of the LSI chip 103.

Further, a plurality of second pad electrodes 125 are placed over themain surface of the LSI chip 103. The respective pad electrodes 125 aredisposed at arbitrary positions around an area where the LSI chip 113 isplaced.

The LSI chip 113 smaller than the LSI chip 103 in size is fixed andplaced on a substantially central area of the LSI chip 103 with anadhesive provided between the back of the LSI 113 and the main surfaceof the LSI chip 103. Incidentally, the main surface of the LSI chip 103may desirably be comprised of an insulating protective film to avoid aneedless electrical connection to the LSI chip 113. A plurality of thirdpad electrodes 115 are placed over the main surface of the LSI chip 113.In the first embodiment, the pad electrodes 115 are respectively placedin line along the two sides (corresponding to the sides along which thesecond pad electrodes 125 are arranged) of the LSI chip 113.

The plurality of first pad electrodes 105 are electrically connected totheir corresponding leads 9 through wires 107. Each of the plurality ofsecond pad electrodes 125 is electrically connected to any of theplurality of third pad electrodes 115 corresponding thereto through awire 117.

The LSI chips 103 and 113, the die 8, the wires 107 and 117, and some ofthe leads 9, which include portions thereof connected to the wires 107,are sealed with a resin 10.

FIG. 3 is a perspective view for describing the assembly of thesemiconductor device shown in FIG. 1. Incidentally, some of the leads 9and wires 107 are omitted from FIG. 3 because FIG. 3 is used for thedescription of its assembly. As shown in FIG. 3, an LSI chip 103 havingfirst pad electrodes 105 and second pad electrodes 125 is firstprepared. Upon the manufacture of the LSI chip 103 at this time, the padelectrodes 125 are configured so as to be placed around an area 103 a ona main surface on which the LSI chip 113 is to be placed subsequently.Further, the LSI chip 113 is additionally manufactured and preparedindependently of the manufacture of the LSI chip 103. At this time, theplacement or layout of pad electrodes 115 may be set according topositions to place the pad electrodes 125 thereat in order to make wirebonding to be executed subsequently easier and avoid a short circuit orthe like developed between wires. The layout of the pad electrodes 125on the LSI chip 103 and the layout of the pad electrodes 115 on the LSIchip 113 can be handled as follows: If either one of both the padelectrodes is determined in advance upon design of a circuit layout usedfor the LSI chip with either one of the pad electrodes placed thereon,the LSI chip with the other pad electrodes placed thereon can also copewith their. placement with ease.

The first pad electrodes 105 of the LSI chip 103 and the leads 9 arerespectively electrically connected to one another by the wires 107.Afterwards, the LSI chip 113 is placed over the area 103 a to be locatedin place, on the main surface of the LSI chip 103. Thereafter, the padelectrodes 115 and the pad electrodes 125 are electrically connected toone another by wire bonding. Incidentally, a method of manufacturing thesemiconductor device is not limited to it. Before the first padelectrodes 105 of the LSI chip 103 and the leads 9 are electricallyconnected to one another by the wires 107 respectively, the LSI chip 113is placed over the area 103 a to be located in place on the main surfaceof the LSI chip 103. Thereafter, the electrical connections between thefirst pad electrodes 105 and the leads 9 by the wires 107 and theelectrical connections between the pad electrodes 115 and the padelectrodes 125 by the wires 117 may be performed. The latter can beexpected to become efficient because a wire bonding process cancollectively carried out.

Thus, the semiconductor device according to the first embodiment is onewherein the LSI chips 103 and 113 are singly developed respectively andthe transfer of signals between these two LSI chips is performed usingthe pad electrodes 125 provided over the LSI chip 103 after thefabrication of the LSI chips, whereby one function (corresponding to afunction used as a system LSI) is implemented.

A typical example of the system LSI applied to the semiconductor deviceof the present invention will be explained using a micon equipped with abatch erasable EEPROM. FIG. 4 is a block diagram showing a configurationof a micon 50 equipped with a batch erasable EEPROM.

As shown in FIG. 4, the micon 50 comprises various components such asperipheral functions such as a CPU 51, a timer 58, a serial-parallelconverter 59, etc., an SRAM 55 used to hold data therein and transmit ittherefrom, a batch erasable EEPRROM 53 used as a programmable memorywith various instructions stored therein, an input/output interface 57,etc.

These respective components are connected to one another so as to becapable of performing the transfer of signals therebetween through theuse of a number of signal lines and buses. A common bus 56 is used totransfer a signal outputted from the timer 58 through a signal line 66and transfer a signal outputted from the serial-parallel converterthrough a signal line 67. Further, the common bus 56 is used to swapdata with the CPU 51 through a signal line 61 and swap addresses anddata with the SRAM 55 through a signal line 62, for example. A signalline 63 transmits control signals such as a write instruction signal,etc. outputted from the CPU 51 to the SRAM 55. The input/outputinterface 57 is used to transfer data received from outside through asignal line 69 to the CPU 51 through a signal line 64. The signal line64 is used to transfer the control signals sent from the CPU 51 to theinput/output interface 57. A signal line 65 is used to transfer dataread from the SRAM 55 to the input/output interface 57 and receive asignal sent from the input/output interface 57. The input/outputinterface 57 performs swapping of signals such as data with the outsidethrough the signal line 69.

The EEPROM 53 sends programs such as instructions stored therein to theCPU 51 through the use of a signal line 68. Further, the EEPROM 53selects a desired program according to each address sent from the CPU 51through the signal line 68. Namely, the signal line 68 comprises pluralsignal lines such as an address bus, a data bus, a memory control signalline, a source voltage supply line for the EEPROM 53, etc.

In the semiconductor device 100 according to the first embodiment of thepresent invention, the LSI chip 113 is defined as a memory system LSIequipped with the EEPROM 53 shown in FIG. 4, whereas the LSI chip 103 isdefined as a Logic system LSI loaded with other components shown in FIG.4 except for the EEPROM 53.

Therefore, the plurality of pad electrodes 115 of the LSI chip 113 andthe plurality of pad electrodes 125 of the LSI chip 103 are respectivelyused to perform signal swapping similar to the signal line 68 shown inFIG. 4. In other words, the plurality of pad electrodes 115 of the LSIchip 113 and the plurality of pad electrodes 125 of the LSI chip 103 areelectrically connected to one another by the wires 117 to thereby makeit possible to implement the signal swapping similar to the signal line68.

As described above, the second pad electrodes 125 provided over the LSIchip 103 serve as electrode pads used to interface with the LSI chip113. The pad electrodes 125 are used to allow the swapping of signalswith the LSI chip 113, thereby making it possible to activate the systemLSI or LSI chip as the micon equipped with the batch erasable EEPROM.Further, any new restrictions are not imposed on the number of theconventional leads and their placement and hence the leads 9 may behandled in a manner similar to the prior art.

In the first embodiment of the present invention, the two LSI chips ofthe LSI chip 103 and the LSI chip 113 held in one package are used tothereby allow them to operate as one micon. Therefore, the semiconductordevice according to the first embodiment of the present invention canobtain the following advantageous effects.

Since the LSI chip 103 used as the first semiconductor element and theLSI chip 113 used as the second semiconductor element can respectivelybe manufactured individually, the respective LSI chip can bemanufactured in parallel. Thus, TAT for development and manufacture canbe shortened.

Since the LSI chip 103 can be manufactured in the Logic process and theLSI chip 113 can be fabricated in a process peculiar to a memory,respectively, it is not necessary to develop a mixed process obtained bya combination of the Logic process and the memory process. Inparticular, an LSI comprised of an LSI-peculiar high-withstand processwhich needs high-withstand elementary devices as in the batch erasableEEPROM, and an LSI comprised of an SOI process can also be utilized incombination, thereby making it possible to implement the development ofa system LSI having a more advanced function.

The semiconductor device is implemented by a laminated layer of the LSIchips, and the layout and the number of the leads 9 may be handled in amanner similar to the LSI chip 103 used as one semiconductor element. Itis therefore unnecessary to increase a size used as for thesemiconductor device and additionally develop a lead frame. Asemiconductor device manufactured in the conventional mixed process canbe applied as it is.

Upon-bringing a micon to the commercial stage, a form having a product(hereinafter called “mask ROM version micon”) using a mask ROM in whichsoftware (program) is fixed as a program memory, and a product(hereinafter called “EEPROM version micon”) using a software-changeableEEPROM even after the program memory is built in LSI, is common uponimplementation of the same function where a circuit portioncorresponding to hardware like a CPU or a DSP (Digital Signal Processor)and a program memory corresponding to software are mixed together toimplement one function. In addition to the above, there are known onewherein an EPROM is provided for software and a package is provided witha window for ultraviolet radiation, an OTP (One Time Programming)version micon which allows program writing only once without providingthe window, etc.

In general, the EEPROM version micon is capable of performing writing ofdata into an EEPROM, i.e., rewriting of software, etc. even after theEEPROM is incorporated into an LSI as a program memory. Therefore, theEEPROM version micon is applied to obtain the following advantageouseffect.

The first is to make it possible to develop and debug softwareimmediately before the shipment of micon's products. The second is tomake it possible to cope with the occurrence of a soft bug and meet animprovement (version-up or the like) in product because it is possibleto rewrite software even after the shipment of micon's products.

Namely, the EEPROM version micon is used for product developmentintended for a new field, which is predicated on the rewriting ofprograms, with a view toward performing the shortening of TAT forproduct development, an improvement in function, etc.

Since, however, a voltage higher than a source voltage is used for thewriting of data, etc., the EEPROM version micon needs a specialmanufacturing process and tends to increase in manufacturing cost.

On the other hand, although there is a small difference according to thetype of mask ROMs to be placed, the mask ROM version micon can bemanufactured by using masks used in a common Logic process, such as ametal layer, a contact layer, an implanted layer, etc. and fabricating afixed program code mask. Therefore, since the mask ROM version micon norequires the special manufacturing process, the manufacturing costthereof can be brought to a low cost (about ½ to ⅓ the manufacturingcost of the EEPROM version micon).

Since there is a difference in manufacturing cost in this way, theEEPROM version micon and the mask ROM version micon are commonly appliedas follows:

Upon development of each micon's product, the EEPROM version micon isfirst used to allow the rewriting of a program. Hardware and softwareare debugged in a state in which the rewriting of the program has beenmade possible.

Immediately after the commencement of the mass production of micon'sproducts, the EEPROM version micon is applied as for mass production.This is carried out to allow the handling of program bugs apt to occurin case of emergency.

Market track records (such as the situation with regard to theoccurrence of program bugs, etc.) are confirmed after the shipment ofeach product as the EEPROM version micon, and the EEPROM version miconis changed to a mask ROM version micon capable of implementing the samefunction under stable conditions.

Thus, the EEPROM version micon is applied upon development and initialmass-production shipment. Therefore, if consideration is given to thenumber of life-cycle shipments of such types of micons, then the maskROM version micon rather than the EEPROM version micon predominates.

Therefore, when the development of micons each having a new function istaken into consideration, the development of the EEPROM version miconreduced in mass-production number must also be carried out together withthe development of the mask ROM version micon. Thus, when the miconshaving the new functions are released, TAT, the number of man-hours, andthe cost of development increase respectively. In particular, the EEPROMversion micon reduced in mass-production number is deteriorated ininvestment efficiency.

Since the EEPROM version micon and the mask ROM version micon need theimplementation of the same function, the EEPROM version micon mustrealize various characteristics equivalent to those of the mask ROMversion micon which takes a final form. The various characteristicsinclude current consumption, latch-up characteristics, noisecharacteristics, etc. as well as electrical characteristics andfunctions. If substantially the same various characteristics are notobtained from the EEPROM version micon and the mask ROM version micon,then a problem arises in that a difference occurs in EMC specs. Aproblem arises in that when the EEPROM version micon is replaced by themask ROM version micon, for example, an operating margin thereofincreases, noise increases, a re-adjustment thereof is required becausethe accuracy of an analog circuit built in the micon varies, the amountof current consumption changes, and the lifetime of a battery changes.

A second embodiment provides one to which the semiconductor deviceaccording to the first embodiment of the present invention is applied,and which is improved so as to solve the above-described problems whicharise between the EEPROM version micon and the mask ROM version micon. Asemiconductor device according to the second embodiment of the presentinvention will be described below with reference to the drawings. FIGS.5 and 6 are respectively plan views of the semiconductor deviceaccording to the second embodiment of the present invention. FIG. 5 is aview showing the semiconductor device used as an EEPROM version micon,and FIG. 6 is a view showing the semiconductor device used as a mask ROMversion micon, respectively. FIGS. 5 and 6 correspond to FIG. 2. Thesame elements of structure as those shown in FIG. 2 are identified bythe same reference numerals.

In FIG. 5, an EEPROM defined as a program memory is placed over an LSIchip 213. An LSI chip 203 having a main surface on which the LSI chip213 is placed, is equipped with a mask ROM defined as a program memoryand with all of circuits required as for a micon other than the programmemory.

A plurality of pad electrodes 225 placed over the main surface of theLSI chip 203 are electrically connected to their corresponding ones of aplurality of pad electrodes 215 placed over a main surface of the LSIchip 213 by wires 217. Further, a plurality of leads 9 are electricallyconnected to their corresponding ones of a plurality of pad electrodes205 by wires 207.

In the LSI chip 203, a selecting pad electrode 205 a is provided as oneof the first pad electrodes 205. In the EEPROM version micon shown inFIG. 5, the pad electrode 205 a is electrically connected to itscorresponding lead 9 a for a source voltage by a wire 207 a. The lead 9a for the source voltage is also connected to its corresponding padelectrode 205 for the source voltage.

The mask ROM version micon shown in FIG. 6 does not have the LSI chip213. Therefore, any of the pad electrodes 225 are not subjected to wirebonding. The LSI chip 203 is equipped with a mask ROM 222. Further, thepad electrode 205 a is not wire-bonded to its corresponding lead 9 a forthe source voltage.

A description will now be made of the relationship between the padelectrode 205 a of the LSI chip 203 and a circuit placed inside the LSIchip 203. FIG. 7 is a view showing the circuit in the LSI chip 203,which is connected to its corresponding pad electrode 205 a.

In FIG. 7, the pad electrode 205 a is electrically connected to agrounded pull-down resistor 251 and electrically connected to one inputterminal of an AND gate 253. A reset signal RES for initialization ofthe micon is inputted to the other input terminal of the AND gate 253through a delay buffer 257. An output terminal of the AND gate 253 iselectrically connected to an input terminal D of a latch circuit(hereinafter called “LAT”) 255. The reset signal RES is inputted to aclock terminal of the LAT 255. A signal outputted from the LAT 255 isinputted to an internal circuit to be described later as a select signalSEL. Incidentally, a flip-flop may be used as the LAT 255 in FIG. 7.Incidentally, the AND gate 253 may not be provided. However, the ANDgate 253 may preferably be provided to stabilize the potential level ofa signal inputted to the input terminal D of the LAT 255. If, forexample, an analog switch whose conduction is controlled based on thereset signal RES, is to receive the signal inputted through the inputterminal D inside the LAT 255, it is then unnecessary to provide the ANDgate 253. If the signal inputted from the input terminal D is to bereceived by an inverter inside the LAT 255, then the AND gate 251 maypreferably be provided because the state of operation of the invertercan reliably be stabilized.

The operation of the circuit shown in FIG. 7 will be described. Nowconsider where the pad electrode 205 a is electrically connected to itscorresponding lead 9 a for the source voltage by wire bonding as shownin FIG. 5. Therefore, a signal having a source potential level(hereinafter called “H level”) is inputted to one input terminal of theAND gate 253. Upon initialization of a micon, the reset signal RESchanges from a ground potential level (hereinafter called “L level”) tothe H level. At this time, the potential level of a signal outputtedfrom the AND gate 253 is brought to the H level. Afterwards, thepotential level of the reset signal RES changes from the H level to theL level with deinitialization of the micon. The LAT 255 captures ortakes in a signal received at the input terminal D in response to thefalling edge of the reset signal RES (H through-L latch type). Owing tothe provision of the buffer 257, the potential level of the signalcaptured by the LAT 255 results in one set according to a potentiallevel at the pad electrode 205 a. As a result, the potential level ofthe select signal SEL corresponding to an output signal of the LAT 255is brought to the H level.

Let's also assume that the pad electrode 205 a is electricallydisconnected from the leads 9 a for the source voltage by wire bondingas shown in FIG. 6. Therefore, the level of the potential applied to oneinput terminal of the AND gate 253 is brought to the L level by thepull-down resistor 251. Thereafter, the potential level of the resetsignal RES changes from the L level to the H level in the same manner asdescribed above. In response to the change of the reset signal RES tothe L level again, the LAT 255 captures a signal received at the inputterminal D. As a result, the potential level of a select signal SELcorresponding to an output signal of the LAT 255 is brought to the Llevel.

Thus, the potential level of the select signal SEL can be selectedaccording to whether the pad electrode 205 a is connected to the lead 9a by wire bonding.

A description will next be made of the circuit lying. within the LSIchip 203, to which the select signal SEL is inputted. FIG. 8 is a viewshowing the concept of a selection circuit 260 to which the selectsignal SEL is inputted, and FIG. 9 is a specific circuit diagram of theselection circuit 260, respectively. Incidentally, FIGS. 8 and 9respectively show an example in which the EEPROM placed on the LSI chip213 and the mask ROM placed on the LSI chip 203 handle 8-bit data.

In FIG. 8, data D0 through D7 sent from the EEPROM placed on the LSIchip 213 are inputted to one input terminal (0 side input) of theselection circuit 260. Further, data D′0 through D′7 sent from the maskROM placed on the LSI chip 203 are inputted to one input terminal (1side input) of the selection circuit 260. While the numbers of signallines for transferring the data D0 through D7 and the data D′0 throughD′7 are respectively shown as one in FIG. 8, 8-bit data are transferredin parallel by eight signal lines. The select signal SEL is inputted tothe selection circuit 260. When the potential level of the select signalSEL is of an L level, signals ID0 through ID7 outputted from theselection circuit 260 result in signals set according to the data D0through D7 respectively. When the potential. level of the select signalSEL is of an H level, data ID0 through ID7 outputted from the selectioncircuit 260 result in signals set according to the data D′0 through D′7respectively.

The above operation will be explained using a specific circuit diagramof the selection circuit 260, which is shown in FIG. 9. The selectioncircuit 260 comprises sixteen two-input one-output AND gates 261-0through 261-7 and 263-0 through 263-7, eight two-input one-output ORgates 265-0 through 265-7, and one inverter 267. Data D'n is inputted toone input terminal of the AND gate 261-n (where n: integers of 0 to 7).A select signal SEL is inputted to the other input terminal of the ANDgate 261-n. Data Dn is inputted to one input terminal of the AND gate263-n. A signal outputted from the inverter 267 supplied with the selectsignal SEL is inputted to the other input terminal of the AND gate263-n. A signal outputted from the AND gate 261-n and a signal outputtedfrom the AND gate 263-n are respectively inputted to two input terminalsof the OR gate 265-n.

As is understood from the configuration of the selection circuit 260shown in FIG. 9, when the potential level of the select signal SEL is Lin level, the AND gates 263-n to which a signal whose potential level isH in level, is inputted from the inverter 267, become effective orvalid. As a result, data D0 through D7 are respectively outputted asoutput data ID0 through ID7 through the AND gates 263-n and OR gates265-n. When the potential level of the select signal SEL is of the Hlevel, the AND gates 261-n to which the select signal SEL whosepotential level is of the H level, is inputted, becomes effective, sothat data D′0 through D′7 are respectively outputted as output data ID0through ID7 through the AND gates 261-n and OR gates 265-n. The outputdata ID0 through ID7 are transferred to an internal bus provided insidethe LSI chip 203 so as to be capable of being transferred to anothercircuit placed within the LSI chip 203.

Thus, if the potential level of the select signal SEL is of the L level,then the mask ROM placed over the LSI chip 203 can selectively be used.If the potential level of the select signal SEL is of the H level, thenthe EEPROM placed on the LSI chip 213 can selectively be used.Incidentally, FIGS. 8 and 9 respectively show only the selection orswitching of a data bus section for performing the transfer of data byway of example. However, it is necessary to allow a selection in amanner similar even to other control signals required to access each ofmemories (mask ROM and EEPROM) in practice. The batch erasable EEPROMneeds a special bus for the writing of data as a distinction from themask ROM. On the other hand, when the LSI chip 213 is selected, the LSIchip 203 is provided with a bus used only upon writing of data into theEEPROM of the LSI chip. Alternatively, the. signal lines fortransferring the data D′0 through D′7 and the signal lines fortransferring the ID0 through ID7, etc. all of which are shown in FIGS. 8and 9, are set as bidirectional buses. In this condition, theconfiguration of the selection circuit 260 can be implemented byhandling such as the setting of it as analog switch other than the ANDand OR gates.

Thus, switching can be performed between an MCP mode for using the LSIchip 213 and a Single Chip mode for using the LSI chip 203 aloneaccording to the presence or absence of bonding to the electrode pad 205a. Namely, the LSI chip 203 equipped with the mask ROM as the programmemory and the LSI chip 213 equipped with the batch erasable EEPROM forthe program memory are utilized in combination in the semiconductordevice according to the second embodiment of the present invention.Thus, when the EEPROM version micon is selected, the LSI chip 203 andthe LSI chip 213 are combined together so as to serve as an MCP, therebymaking it possible to operate it as a micon. When the mask ROM versionmicon is selected, it can be operated as a micon by using the LSI chip203 alone without being utilized as an MCP using the LSI chip 213.

Owing to such a configuration, the semiconductor device according to thesecond embodiment of the present invention can obtain the followingadvantageous effects in addition to the effects obtained by thesemiconductor device according to the first embodiment.

The first resides in that since the LSI chip 213 of the MCP type EEPROMcan be designed aside from the LSI chip 203, the EEPROM version miconcan also be implemented simultaneously by simply newly designing the LSIchip 203 corresponding to the mask ROM version micon. Namely, since itis not necessary to individually develop the EEPROM version micon andthe mask ROM version micon respectively, the shortening of developmentTAT and a reduction in the cost of development can be achieved. Sincethe LSI chip 213 of the MCP type EEPROM can be applied even to variousmicons without being limited to a specific micon, a reduction indevelopment cost can be expected.

The second resides in that since the LSI chip 203 used as the mask ROMversion micon is used as a base even in the case of the EEPROM versionmicon, a difference in various characteristics such as electricalcharacteristic, noise characteristics, etc. can extremely be reduced byapplying a common circuit to a configuration other than a programmemory. As a result, it is easily feasible to provide the EEPROM versionmicon and the mask ROM version micon which produce no difference in EMCspecs.

The third resides in that as compared with the case in which the EEPROMversion micon is implemented by application of a special manufacturingprocess thereto as in the prior art, an EEPROM unit can be implementedby applying the conventional high-withstand process thereto and othermicon's circuit units can be implemented by applying the conventionalMOS process thereto. Therefore, the EEPROM version micon can beimplemented at a further reduced cost.

The fourth resides in that the replacement of the LSI chip 213 withanother makes it possible to develop micons adapted to various specs ina short period of time. Micons different in, for example, memory size,the number of times that the rewriting of a batch erasable EEPROM isassured, operating voltage, etc. can be implemented by simply newlydeveloping the LSI chip 213.

Incidentally, the second embodiment has been described by applying theLSI chip 203 as the mask ROM version micon. However, a micon free of aprogram memory, i.e., having no mask ROM is developed as the LSI chip203, and each of a mask ROM micon and a batch erasable EEPROM micon isdeveloped as the LSI chip 213. Thereafter, the mask ROM version miconand the EEPROM version micon may be implemented by applying any of themthereto as the program memory. Since, in this case, the pad electrodes225 are electrically connected to their corresponding pad electrodes 215of the LSI chip 213 in either case, the circuits and the like shown inFIGS. 7 through 9 become unnecessary. The LSI chip 213 utilized incombination with the LSI chip 203 used as the mask ROM version micon isnot limited to the batch erasable EEPROM and may be a mask ROM or anEPROM or the like. When, for example, the capacity of a mask ROM placedover the already-developed LSI chip 203 lacks, a mask ROM large inmemory capacity is developed through the LSI chip 213 without newlydeveloping the LSI chip 203, and the LSI chip 203 makes use of the maskROM of the LSI chip 213, thereby making it possible to easily cope withthe lack of the memory capacity.

The first and second embodiments of the present invention have beendescribed in detail above. Particularly, the second embodiment hasdescribed the LSI chip 203 as the mask ROM version micon and the LSIchip 213 as the batch erasable EEPROM for the program memory. However,the following can be applied as the LSI chip 213.

(1) One equipped with a batch erasable EEPROM and an analog circuit suchas an analog digital converter or the like

(2) Analog circuit such as an analog-digital converter or the like

(3) One equipped with a batch erasable EEPROM and an SRAM

(4) Mask ROM

(5) DRAM

(6) SRAM

(7) EEPROM

A low voltage (e.g., source voltage Vdd=1.6V to 2.0V in a 0.18 μmprocess) is used in a Logic process. employed in a micon or the like,for example. On the other hand, a circuit unit such as an analog-digitalconverter or the like, which handles an analog signal, needs to maintainthe conventional interface level (5V or 3V) used in a sensor, anactuator, etc. The above (1) and (2) can sufficiently cope with it.Described specifically, a mask ROM version micon excluding an analogcircuit is developed as the LSI chip 203. As the LSI chip 213, a systemLSI is implemented by applying the circuit shown in the above (2) andcombining these LSI chips together as the MCP type as described in thefirst or second embodiment. In the case of an EEPROM version micon, theabove (1) may be applied as the LSI chip 213. In this case, the mask ROMversion micon may be brought to the commercial stage as a miconunequipped with the analog circuit without developing the above (2).

Further, the above (3) can be used to simultaneously implement theaddition of memories for data storage in the second embodiment. In thiscase, the SRAM of the LSI chip 213 is used as an add-in memory for datastorage, and the batch erasable EEPROM is used as a program memory.

Further, the above (4) to (7) are applied for implementation as for theaddition of data storage memories placed on the LSI chip 203 and formixed loading of memories, which serves as a manufacturing processdifferent from that for the LSI chip 203. When, for example, a space forthe data storage memory placed in the LSI chip 203 is exceeded, anaddress control signal and a chip select signal may be controlled sothat accessing is shifted to the add-in memory for data storage placedwithin the LSI chip 213. If done in this way, then a desired system LSIcan be implemented in a short period of time without an increase inproduct's cost.

Incidentally, the first and second embodiments have shown the MCP typesemiconductor device implemented as the system LSI by using the two LSIchips and interconnecting them with each other. It is needless to saythat three or more LSI chips may be interconnected with one another toform a semiconductor device which implements a function set as a systemLSI. For example, four LSI chips comprising an LSI chip used as a maskROM version micon, an LSI chip used as a batch erasable EEPROM, an LSIchip used as a power control circuit, and an LSI chip used as acommunication analog LSI may be interconnected with one another andaccommodated in one package to implement a function set as a system LSI.

The system LSIs typified by the micons have been described by way ofexample in the first and second embodiments. However, the presentinvention is not necessarily limited to those. The present invention isapplicable even to the following cases as applications of the presentinvention.

For example, a plurality of LSI chips difficult for fabrication thereofon the same semiconductor substrate, which is one gist or substance ofthe present invention, and different in manufacturing process, may beinterconnected with one another to implement an LSI. For example, apower LSI to which a bipolar process is applied, and an LSI to which aLogic process used for control of the power LSI is applied, may beconnected to each other and held in one package.

Further, the present invention can be applied even among a plurality ofLSI chips (any of them being one to which the Logic process is applied)capable of being manufactured on the same semiconductor substrate andsimilar in manufacturing process. For example, a communication LSIalready developed and equipped with a number of analog circuits eachoperable as a single LSI, and a micon used for controlling thecommunication LSI may be interconnected with each other and held in onepackage. If done in this way, then different LSIs with high added valuescan be developed in a short period of time.

Thus, it is of importance that in either case, a plurality of LSI chipsheld in one package are interconnected with one another so as to allowthe transfer of data or the like, and a desired function defined as asemiconductor device is implemented by these plural LSIs.

In the second embodiment, the circuit placed within the LSI chip 203selectively determines the use of the LSI chip 213 according to thepresence or absence of wire bonding effected on the pad electrode 205 a.However, the present invention is not necessarily limited to it. Aselection similar to the above can be implemented even by other methodsto be next described.

The first is a method of performing a chip selection using a mask layerfor a mask ROM employed in the LSI chip 203. Namely, as a mask layer fordetermining a code (program) employed in the mask ROM, may be mentioned,various layers such as a metal layer, a contact layer, an implantedlayer, etc. according to the type of memory. The mask ROM is fabricatedusing a desired mask corresponding to the program code. Therefore, themask for the mask layer is used as for the above selection in additionto one for the code used in the mask ROM to thereby allow the selectionand designation of an LSI chip. If the LSI chip 213 is selected andprocessed for the purpose of its use in this case, then the LSI chip 203cannot be used singly. However, if done in the above-described manner,it is then unnecessary to provide a special pad electrode for selection,such as the pad electrode 205 a. Since the code mask used for the maskROM can be shared for the selection, it is possible to prevent anincrease in cost due to an increase in the number of masks, etc., and anincrease in manufacturing process.

Next, there is known a method of performing a chip selection using afuse ROM. Namely, a fuse (hereinafter called “fuse ROM”) comprised of ametal wire capable of being broken by causing a predetermined current toflow therethrough or by laser is placed within the LSI chip 203.Thereafter, the corresponding LSI chip may be selected according to thebroken state thereof. If a description is made by the example shown inFIG. 7, then such a configuration that a source voltage is appliedthrough the fuse ROM used in place of the pad electrode 205 a is taken.The application of the source voltage to an AND gate and the applicationof the ground voltage thereto through the pull-down resistor 251 mayselectively controlled according to the broken state of the fuse ROM.Since a selecting process can be done upon wafer probing of the LSI chip203 if such a configuration is taken, flexible handling can be achievedif consideration is given to control on stocks, etc.

Next, a method of setting a predetermined pad electrode 205 of the LSIchip 203 as a pad electrode dedicated to selection is known. This is onewherein the pull-down resistor 251 shown in FIG. 7 is omitted, the padelectrode 205 a is electrically connected to its corresponding leaddedicated to selection, and a selecting process is done according to theapplication of a source voltage to the lead or the application of aground voltage thereto. If done so, then a mask ROM version micon and anEEPROM version micon can be easily selected even after a semiconductordevice held in a package has been built in an electronic device orapparatus. As a result, device's debugs and difference evaluations withrespect to the mask ROM version micon and the EEPROM version micon canbe implemented with satisfactory accuracy and at low cost.

As the method of providing the lead and pad electrodes dedicated toselection as described above, different programs may be incorporatedinto the LSI chip 203 and the LSI chip 213 respectively. Namely, miconscapable of implementing different operations corresponding to differentprograms can be selectively implemented according to the potential levelof a signal supplied to a selection-dedicated lead. In other words, onemicon can be utilized according to two types of uses as a package. Sincethe electronic device to which such a semiconductor device is applied,can perform switching. to the micon without turning off the power, forexample, the succession of each program stored in the mask ROM of theLSI chip 203 may sequentially be executed by each program stored in theEEPROM of the LSI chip 213. After the LSI chip 203 for one micon (maskROM version micon) has been developed, the LSI chip 213 can be set up asan applied product of the micon by its development.

Next, there is known a method of selecting an LSI chip according to theprogram stored in the mask ROM of the LSI chip 203 or the program storedin the EEPROM of the LSI chip 213. Namely, a program-based start-up atan initial operation (default) of a micon wherein the LSI chip 203 andthe LSI chip 213 are held in one package, is determined based on eitherof the program stored in the mask ROM of the LSI chip 203 and theprogram stored in the EEPROM of the LSI chip 213. Thereafter, a decisionas to which LSI chip should be used (which program of LSI chip should beused), may be performed according to the initial program routine for theselected program of LSI chip. For example, the potential level of thesignal inputted from the above-described selection lead is confirmedbased on the start-up program used as the program routine, and theresult of confirmation thereof is held by a mode designation register orthe like built in a micon according to the result of confirmationthereof. Afterwards; the result of its confirmation may be used as aselect signal indicative of which program of LSI chip should be used.

Incidentally, a method of confirming the state of the register referredto above may be used as the method of selecting the corresponding chipaccording to another program used as the start-up program. Such a methodis feasible if a register set or reset according to whether the LSI chip213 is connected to the LSI chip 203 so as to allow the transfer of datatherebetween, is such a register as to hold a flag indicative of thestate of the register.

Next, there is known a method of performing a chip selection by hardwaresuch as a determination circuit or the like for making a decision as towhether the LSI chip 213 is connected to the LSI chip 203 so as to allowthe transfer of data therebetween. Namely, such a determination circuitdetermines the presence or absence of the LSI chip 213 upon micon'sinitialization or the like. When the LSI chip 213 is judged to beabsent, a program on the LSI chip 203 side may be started up. When theLSI chip 213 is judged to be present, a program on the LSI chip 213 sidemay be started up. One similar to such a configuration as shown in FIG.7 is applicable as this type of determination circuit. This may beconnected to a desired judgeable signal line without being connected tothe pad electrode 205 a. The decision of such a determination circuitmay be performed by accessing to a predetermined register via a bus lineor by connecting desired pad electrodes of two LSI chips to each otherby determining/detecting wires or the like and utilizing such aconnected state (e.g., corresponding to one in which, for example, asource voltage is applied when they are being connected to each other,and an open state is reached when they are not connected to each other).

A description has been made in detail of the modifications andapplications related to the combination of the two LSI chips and theselecting process thereof employed in the first and second embodiments.Modifications and applications related to layouts such as the layout ofpad electrodes, etc. will next be described below.

In the first and second embodiments, the pad electrodes 125 and the padelectrodes 225 are placed in areas (substantially central positions indistances between parallel outer peripheral sides of the two LSI chipsin the drawings) relatively close to the outer peripheries of the LSIchips 113 and 213 as shown in FIGS. 2 and 5. As represented by a planview of FIG. 10, pad electrodes 325 are further placed in theircorresponding positions closer to the outer periphery of the LSI chip.113 as viewed from the outer periphery of the LSI chip 103 within anarea in which the LSI chip 113 is placed. In the placement of such padelectrodes, wires 107 for respectively connecting leads 9 and padelectrodes 105 and wires 117 for respectively connecting pad electrodes115 and the pad electrodes 325 do not intersect each other. However, thefollowing problems are taken into consideration.

A first point resides in that when the size of the LSI chip 113 placedover a main surface of the LSI chip 103 is changed, handling associatedwith the size change becomes difficult or allowance therefor is reduced.Such a size change is considered to be sufficiently within the bounds ofpossibility that it will be developed due to specs changes such as anincrease in memory size, etc., and a change in manufacturing process tobe applied.

A second point resides in that since the pad electrodes 125 and 325 orthe like are respectively placed in areas close substantially to thecenters of the LSI chips 103, restrictions such as the difficulty ofplacement or layout of protection circuits for these pad electrodes 125and 325 or the like, an increase in needless area, the division of acircuit module employed in the LSI chip 103 by the areas for theplacement of the pad electrodes 125 and 325, etc. might be imposed onlayout design of the LSI chip 103, Such restrictions make it impossibleto efficiently perform the layout design of LSI by application of thenormally-used CAD system.

Such a layout of pad electrodes as shown by a plan view of FIG. 11 canbe applied to solve such a problem. In FIG. 11, elements of structuresimilar to those shown in FIG. 10 are identified by the same referencenumerals.

In FIG. 11, pad electrodes 425 equivalent to the pad electrodes 125 and325 are placed in staggered form with pad electrodes 105 at theircorresponding positions close to the outer periphery of an LSI chip 103as viewed from the outer periphery of an LSI chip 113. Otherconfigurations are similar to those shown in FIG. 10. Thus, since thepad electrodes 105 for connection to leads and the pad electrodes 425for connection to pad electrodes 115 are alternately placed in staggeredform, the above-described problem can be solved and an efficient layoutcan be implemented in space-saving form.

Next, any of the above embodiments and modifications or the like hasshown, as an example, the case where the pad electrodes are respectivelyplaced over only the two sides of the LSI chip 103 and the LSI chip 113.No limitation is imposed to this. An example may be used in which asshown by a plan view of FIG. 12 by way of example, pad electrodes 505equivalent to the pad electrodes 105 are placed along the four sides ofan LSI chip 503 equivalent to the LSI chip 103, and pad electrodes 515equivalent to the pad electrodes 115 are placed along the four sides ofan LSI chip 513 equivalent to the LSI chip 113. Pad electrodes 525equivalent to the pad electrodes 125 are placed in staggered formtogether with the pad electrodes 505 in accordance with the placement ofthe pad electrodes 115. The pad electrodes 505 are electricallyconnected to their corresponding leads 9 by wires 507, and the padelectrodes 515 are electrically connected to their corresponding padelectrodes 525 by wires 517.

The pad electrodes shown in FIG. 12 are laid out along the four sides ofthe respective LSI chips in terms of the relation between the size ofthe LSI chip 503 and the size of the LSI chip 513, the number of the padelectrodes 525, and design restrictions on the mounting of these padelectrodes 525 for wire bonding. However, if practicable, it is thendesirable to place pad electrodes 615 equivalent to the pad electrodes515 so as to concentrate on the opposed two sides of an LSI chip 613equivalent to the LSI chip 513, and place pad electrodes 625 equivalentto the pad electrodes 525, of an LSI chip 603 equivalent to the LSI chip503 along the opposed two sides of the LSI chip 603 as shown by a planview of FIG. 13.

The following advantageous effects can be expected by placing the padelectrodes as shown in FIG. 13. A predetermined distance is required tobe ensured in terms of mounting due to restrictions at wire bonding asthe distance between the pad electrode 615 and pad electrode 625 usedfor an internal interface, for example. Since, however, theaforementioned restrictions are not imposed on the sides free of theplacement of such pad electrodes 615, the outer peripheral portion ofthe LSI chip 613 can be brought closer to the neighborhood of padelectrodes 605 for connection to leads. For example, such aconfiguration as shown by a plan view of FIG. 14 can be taken.

It will be understood from FIG. 14 that the size of an LSI chip 613,which extends in the horizontal direction as viewed in the drawing,increases. Namely, a distance (L2) between the side of the LSI chip 613on the non-placement side of pad electrodes 615 and the side of an LSIchip 603 on the non-placement side of the pad electrodes 625 is shorterthan a distance (L1) between the side of the LS chip 613 on theplacement side of pad electrodes 615 and the side of the LSI chip 603 onthe layout side of the pad electrodes 625.

Therefore, the degree of freedom of design and form increases becausethe embodiments shown in FIGS. 13 and 14 provide less restrictions onthe size and form of the LSI chip 613 as compared with the embodimentshown in FIG. 12. If the size of the LSI chip 613 can be brought ascloser to the size of the LSI chip 603 as practicable, then a thickportion increases correspondingly and hence the resistance to anexternal stress can also be further increased.

Incidentally, FIGS. 13 and 14 have respectively shown, as examples, thecases in which the pad electrodes 615 and the pad electrodes 625 for theinterface are respectively placed over the two sides. However, the padelectrodes 615 and the pad electrodes 625 for the interface may beplaced over three sides or one side.

Thus, signals for these pad electrodes 625 can be collectively laid outover the LSI chip 603 by bringing the sides on which the pad electrodes615 and pad electrodes 625 for the interface are placed, into focus. Itis therefore possible to carry out efficient wiring and simultaneouslytest these LSI chip 613 in plural form upon wafer probing of the LSIchip 613.

A description will next be made below of a modification about a test onthe semiconductor device of the present invention. In the presentinvention, a plurality of LSI chips held in one package are used toimplement a desired function in an MCP type semiconductor device.Therefore, whether or not the desired function is properly executed, istested using the leads 9 upon testing on the post-assembly semiconductordevice, whereby the selection of either a non-defective product or adefective product can be carried out. In the semiconductor device of thepresent invention, for example, a test circuit capable of individuallytesting the LSI chip 103 and the LSI chip 113 respectively may morepreferably be built in the LSI chip 103, for example. The desiredfunction is made possible by providing a test function of allowing theinput of a signal having a predetermined potential level to one lead 9for providing test instructions and one pad electrode 105 for providingtest instructions and permitting each individual tests. In such a case,the input/output lead of the leads 9 may be controlled based on thistest signal so as to be selectively connected to an input/output signalof the LSI chip 103 and an input/output signal of the LSI chip 113 bythe selection circuit shown in FIG. 9. By doing so, the LSI chip 113comprised of the batch erasable EEPROM, for example, can be tested by amemory tester using the leads 9, and the LSI chip 103 can be generallytested by a Logic tester. It is thus possible to improve coverage forthe test.

A description will next be made below of a modification related to wirebonding employed in the semiconductor device of the present invention.In the first and second embodiments, the pad electrodes for source andground and the like, of the pad electrodes 115 of the LSI chip 113 arealso electrically connected to their corresponding pad electrodes 125.However, a problem arises in that consideration is given to the factthat the pad electrode for source, the pad electrode for ground and thepad electrode for the analog signal, of the pad electrodes 115 are underthe influence of noise, and when the amount of current increases as inthe case of the pad electrode for source on occasion, portions connectedto these pad electrodes employed in the LSI chip 103 increase in layoutand desired performance cannot be implemented.

In order to cope with such a problem, pad electrodes 515 x and 515 yshown in FIG. 12 may be electrically connected directly to theircorresponding leads 9 x and 9 y by wires 517 x and 517 y. In FIG. 12,for example, the pad electrode 515 x corresponds to a pad electrode forsource, the pad electrode 515 y corresponds to a pad electrode forground, the lead 9 x corresponds to a lead for source, and the lead 9 ycorresponds to a lead for ground, respectively. Further, a pad electrode615 x equivalent to the pad electrode 515 x and a pad electrode 615 yequivalent to the pad electrode 515 y are shown even in FIG. 13.

Since the leads 9 x for source and the leads 9 y for ground arerespectively electrically connected directly to the pad electrodes forsource and the pad electrodes for ground, of the LSI chips 515 and 615by wire bonding as shown in FIGS. 12 and 13, the above-described problemcan be solved. Thus, since noise developed in a source system can beprevented from being passed around and the supply of power or the likethrough internal wires or interconnections of the LSI chips 503 and 603becomes unnecessary, it is also unnecessary to ensure a metal width ofeach wire for coping with a large current flowing in each of the LSIchips 503 and 603.

As to the analog-signal pad electrode of the pad electrodes 115 in theLSI chip 113, a lead 9 w for an analog signal and a pad electrode 815 wfor the analog signal are electrically directly connected to each otherby a wire 717 as shown by a plan view of FIG. 15. If done in this way,then the above-described problem can be solved. The ground pad electrodeemployed in the LSI chip 113 can also be handled as in the relationbetween the pad electrode 815 w and the lead 9 w shown in FIG. 15.

The placement of oscillator circuits in the semiconductor device of thepresent invention will next be described below. When the LSI chip 103and the LSI chip 113 respectively need different source oscillationclocks from the viewpoint of the placed circuits, it is necessary tobuild the oscillator circuits in their corresponding LSI chips andconnect crystal oscillators thereto respectively. Since, in this case,the length of a wire extending to its corresponding lead becomes longand the component of a coil increases in the oscillator circuit on theLSI chip 113 side, the influence of induction becomes large.

In such a case, the oscillator circuit for the LSI chip 113 may beprovided on the LSI chip 103 side. Even though the LSI chip 113 isequipped with the oscillator circuit, the oscillator circuit for the LSIchip 113, which is used as an alternative to one for the LSI chip 103,may input a desired clock to the LSI chip 113 without using theoscillator circuit placed on the LSI chip 113.

A structure of the semiconductor device of the present invention willnext be explained below. Even in the case of any of the above-describedembodiments, for example, the LSI chip 103 large in chip size is placedbelow and the LSI chip 113 small in chip size is placed over the LSIchip 103. As in the batch erasable EEPROM, the application of stress toa portion above each memory cell exerts an influence on circuit'svarious characteristics such as endurance characteristics, etc. An LSIchip susceptible to the stress may always be laid out as one placed onthe upper side of, for example, two LSI chips as a layout capable ofcarrying out a further reduction in the influence of the stress as inthe case of the LSI chip 113.

While the present invention has been described in detail above, it isneedless to say that various improvements and changes can freely be madewithin the scope not departing from the substance thereof.

While the pad electrodes 505 and the pad electrodes 525 are laid out instaggered form in FIG. 12, for example, no limitation is imposed to thislayout. The layout shown in FIG. 12 is applied to cases where in termsof restrictions on the layout, the interval between the adjacent padelectrodes 505 placed within the LSI chip 503 is narrow and theplacement of a protection circuit with respect to the pad electrodes 525is limited. When the limitation on the placement of the protectioncircuit for the pad electrodes 525 is lifted and the interval betweenthe adjacent pad electrodes 505 employed in the LSI chip 503 can be setrelatively wide (to an area corresponding to such an extent that otherpad electrodes can be respectively placed between the adjacent padelectrodes 505, for example), the pad electrodes 525 may be placedbetween the adjacent pad electrodes 505 respectively. Namely, the padelectrodes 505 and the pad electrodes 525 may be placed in line in a rowat the respective sides around the outer periphery of the LSI chip 503.Since, in this case, the wires for source and ground laid out in theneighborhood of these pad electrodes 505 can be shared between theprotection circuit for the electrodes 505 and the protection circuit forthe electrodes 525, they are more effective.

While the second embodiment has shown an example using such a circuit asshown in FIG. 7, the present invention is not limited to such a circuitconfiguration as shown in FIG. 7. When it is desired to set thepotential level of the select signal SEL to the reverse of theabove-described one, for example, the pull-down resistor 251 is used asa pull-up resistor placed between the source potential and the padelectrode 205 a and the pad electrode 205 a may be selected according towhether it is connected to a lead for ground by a wire. This can beimplemented even when the following configuration is taken.

FIG. 19 shows a modification of the circuit shown in FIG. 7. In FIG. 19,the same elements of structure as those shown in FIG. 7 are identifiedby the same reference numerals.

In FIG. 19, an N channel MOS transistor 851 is provided as analternative to the pull-down resistor 251 shown in FIG. 7. Otherelements of structure in FIG. 19 are similar to those shown in FIG. 7.One electrode (e.g., drain) of the MOS transistor 851 is electricallyconnected to a pad electrode 205 a, and the other electrode (e.g.,source) is grounded. A reset signal RES is inputted to a gate electrodeof the MOS transistor 851 through a buffer 257.

Owing to such a circuit configuration as shown in FIG. 19, when thepotential level of the reset signal RES becomes an H level, the MOStransistor 851 is brought into conduction. If the pad electrode 205 a iselectrically connected to a lead 9 a for source by a wire at this time,then a signal whose potential level is of an H level, is inputted froman AND gate 253 to a LAT 255. In order to reliably execute it, anon-resistance of the MOS transistor 851 at the time that it is broughtinto conduction may desirably be set to a high resistance as in thepull-down resistor 251. If the pad electrode 205 a is not electricallyconnected from the lead 9 a through. the wire, then a signal whosepotential level is an L level, is inputted from the AND gate 253 to theLAT 255. Thereafter, a select signal SEL having a potential levelcorresponding to the potential level of the signal inputted to the LAT255 is outputted from the LAT 255. Even if the potential level of thereset signal RES is returned to the L level, the LAT 255 can maintainthe potential level of the select signal SEL. Thus, it is possible tocarry out a selection similar to the second embodiment.

As compared with the circuit shown in FIG. 7, the circuit shown in FIG.19 can reduce a current flowing between the pad electrode 205 a and theground through the use of the MOS transistor 851 except for resetprocessing (i.e., except when the potential level of the reset signalRES reaches the H level) even it the pad electrode 205 a is electricallyconnected to the lead 9 a by the wire. Therefore, the circuit shown inFIG. 19 is capable of reducing power consumption as compared with thecircuit shown in FIG. 7. If the resistor 251 is considered to serve as aMOS resistor, there is no difference in layout between the circuit shownin FIG. 19 and that shown in FIG. 7, and the number of elements remainsunchanged.

There is also known a method unusing such a circuit as shown in FIG. 7.FIG. 20 is a plan view showing an internal structure of an MCP typesemiconductor device showing a modification of the second embodiment ofthe present invention. FIG. 20 corresponds to FIG. 5. In FIG. 20,elements of structure similar to those shown in FIG. 5 are identified bythe same reference numerals as in FIG. 5.

In FIG. 20, a pad electrode 205 b is additionally provided in additionto the configuration shown in FIG. 5. The pad electrode 205 b is placedin such a position as to be connectable to its corresponding lead 9 bfor ground by a wire.

FIG. 21 is a diagram showing a circuit of an LSI chip 203, which isconnected to the pad electrodes 205 a and 205 b employed in themodification shown in FIG. 20.

As shown in FIG. 21, the LSI chip 203 is provided with a buffer 853 asan alternative to such a circuit as shown in FIG. 7. The pad electrode205 a and the pad electrode 205 b are electrically connected to an inputterminal of the buffer 853 through a common wire. Namely, the padelectrode 205 a and the pad electrode 205 b are wired-OR within the LSIchip 103, followed by connection to the input of the buffer 853. Asignal outputted from the buffer 853 is used-as a select signal SEL.

Owing to such a configuration as described above, if the pad electrode205 a is electrically connected to its corresponding lead 9 a for sourceby a wire and the pad electrode 205 b is in an open state without beingelectrically connected to its corresponding lead 9 b for ground by awire, then the potential level of the select signal SEL corresponding tothe output of the buffer 853 is maintained at an H level. If the padelectrode 205 a is in at open state without being electrically connectedto its corresponding lead 9 a for source by a wire, and the padelectrode 205 b is electrically connected to its corresponding lead 9 bfor ground by the wire, then the potential of the select signal SELcorresponding to the output of the buffer 853 is brought to an L level.Thus, a selection similar to the second embodiment can be carried out.

Since the circuit shown in FIG. 7 becomes unnecessary although the padelectrode 205 b is additionally provided by doing in this way, such aconfiguration can contribute to a reduction in the cost of the LSI chip203, the scale-down of its size, etc.

When no pad electrode 205 b is provided, the input terminal of thebuffer 853 is connected to the pad electrode 205 a alone and a signaloutputted from the buffer 853 may be set as the select signal SEL. Inthis case, it is desirable that in order to facilitate wire bonding andprevent a short-circuit developed between wires, the source lead 9 a andthe ground lead 9 b are placed so as to adjoin each other, and the padelectrode 205 a is placed between a source pad electrode 205 d and aground pad electrode 205 g. Thus, the potential level of the selectsignal SEL can be selectively controlled by wire-bonding the padelectrode 205 a to either the source lead 9 a or the ground lead 9 b.

In order to reduce miswire bonding to the pad. electrode 205 a at itsmanufacture, a source lead 9 a and a ground lead 9 b shown in FIG. 22may preferably be placed away from each other. It is necessary toeventually provide the pad electrode 205 a and the pad electrode 205 bas shown in FIG. 20 for the purpose of coping with it.

Further, the following method is also taken into consideration as themethod using the pad electrode 205 a and the pad electrode 205 b.

It is a method of allowing a selective connection between the inputterminal of the buffer 853 shown in FIG. 21 and the ground by using themask layer for the mask ROM employed in the LSI chip 203. Namely, asdescribed above, the various layers such as the metal layer, contactlayer, implanted layer, etc. are known as the mask layer for determiningthe code (program) employed in the mask ROM. The mask ROM is fabricatedusing a desired mask corresponding to the program code. Therefore, themask for the mask layer is used as for the above selection in additionto one for the code used in the mask ROM to thereby allow the selectionand designation of each LSI chip. If the input terminal of the bufferand the ground are connected to each other by the mask layer, forexample, then the potential level of the select signal SEL can be fixedto an L level. In this case, the pad electrode 205 a and the padelectrode 205 b can both be set open without being electricallyconnected to desired leads by wire bonding. Therefore, when the use ofthe semiconductor device as the mask ROM version micon is nowdetermined, the above-described problem can be solved if the potentiallevel of the select signal SEL is fixed by the mask layer. Since themask for the program code is used in this case, an increase inmanufacturing process and an increase in manufacturing cost do not occureither.

When the use of the semiconductor device as the mask ROM version miconis now determined, it is effective to use the pad electrode 205 a, thepad electrode 205 b and the buffer having the input terminal to whichthe pad electrodes 205 a and 205 b are connected, and ground the inputterminal of the buffer by the mask layer. A method of meeting a requestto such a micon, that it is desired to apply the EEPROM version miconagain, will be explained below.

The use of such a circuit as shown in FIG. 23 is effective for such ademand. Since FIG. 23 can be seen in association with FIG. 1, elementsof structures shown in FIG. 23 similar to those shown in FIG. 19 areidentified by the same reference numerals as those in FIG. 19.

The AND gate 253 shown in FIG. 19 is omitted from the circuit shown inFIG. 23. This is based on the reason mentioned in FIG. 7. A LAT 255, abuffer 257, and a MOS transistor 851 similar to those shown in FIG. 19are provided as an alternative to the buffer 853. A pad electrode 205 aand a pad electrode 205 b are wired-OR by a wire within an LSI chip 103and connected to an input terminal D of the LAT 255. A reset signal RESis inputted to a gate terminal of the LAT 255 and inputted to a gateelectrode of the N channel MOS transistor 851 through the buffer 257.One electrode (e.g., source) of the N channel MOS transistor 851 isgrounded and the other electrode (e.g., drain) thereof is connectable tothe input terminal D of the LAT 255 through a switch unit or means 861shown in FIG. 23, which selectively performs their connections throughthe use of the mask layer for the mask ROM previously described. Asignal outputted from an output terminal O of the LAT 255 results in aselect signal SEL. The circuit shown in FIG. 23 is basically similar inoperation to that shown in FIG. 19.

The operation of the circuit shown in FIG. 23 will next be explained.This will be explained on condition that when the potential level of theselect signal SEL is an L level, the semiconductor device using the LSIchips 103 and 113 each equipped with the circuit shown in FIG. 23 is setas the mask ROM version micon and when the potential level of the selectsignal SEL is an H level, the semiconductor device is controlled as theEEPROM version micon. In FIG. 23, the potential level of the selectsignal SEL can selectively be set based on the reset signal RESaccording to whether the pad electrode 205 a is wire-bonded to itscorresponding source lead 9 a or the pad electrode 205 b is wire-bondedto its corresponding ground lead 9 b in a state in which the switch unit861 is disconnected (i.e., in a state in which the MOS transistor andthe input terminal D of the LAT 255 are electrically disconnected fromeach other within the mask layer). In this case, the semiconductordevice can be selected even as either the EEPROM version micon or themask ROM version micon by wire bonding. If the switch unit 861 is turnedon (i.e., if the MOS transistor and the input terminal D of the LAT 255are in an electrically-connected state within the mask layer), and thepad electrode 205 a and the pad electrode 205 b are both set openwithout being subjected to wire bonding, then the potential level of theselect signal SEL can be fixed to an L level even if an attempt is madeto set the potential level of the select signal SEL, based on the resetsignal RES. In this case, the semiconductor device is fixed as the maskROM version micon.

Further, when the pad electrode 205 a is electrically connected to itscorresponding source lead 9 a by the wire in a state in which the switchunit 861 is in the connected state (i.e., when the MOS transistor andthe input terminal D of the LAT 255 are in the electrically-connectedstate within the mask layer), the potential level of a signal inputtedto the input terminal D of the LAT 255 can be brought to an H level.Therefore, even if the switch unit 861 is held in the connected state,the potential level of the select signal SEL can be brought to the Hlevel, based on the reset signal RES. In this case, one fixed as themask ROM version micon can be forcefully reused as the EEPROM versionmicon.

Using the circuit shown in FIG. 23 can solve the above-describedproblem. Further, the circuit shown in FIG. 23 is capable ofcontributing even to a reduction in power consumption in a mannersimilar to FIG. 19.

Incidentally, any of the circuits shown in FIGS. 7, 19 and 23 performsthe setting of the potential level of the select signal SEL, based onthe reset signal RES. Therefore, such a case that the potential level ofthe reset signal RES whose potential level was of the L level, istemporarily brought to the H level and restored to the L level again,can happen due to unexpected events such as an instantaneous break of apower supply, etc. When it is desired to more reliably obtain thestabilization of the potential level of the select signal SEL in such acase, it is desirable to use, for example, the circuit shown in FIG. 21rather than the use of the circuits shown in FIGS. 7, 9 and 23, or setthe potential level of the select signal SEL regardless of other resetsignals RES referred to above.

As a method using the pad electrode 205 a alone without the padelectrode 205 b without having to use the reset signal RES, thefollowing one can also be provided.

The present method is identical to the aforementioned one in that, forexample, an input terminal is connected to a pad electrode 205 a and anoutputted signal is used as a select signal SEL. This is a method ofallowing selective connections between the pad electrode 205 a andground through the use of the mask layer for the mask ROM employed inthe LSI chip 203 in place of the non-provision of a pad electrode 205 b.If, for example, the pad electrode 205 a is set open without beingsubjected to wire bonding and a mask layer is used to connect betweenthe pad electrode 205 a and ground, then the potential level of theselect signal SEL can be set to an L level. If the pad electrode 205 ais electrically connected to a source lead 9 a by a wire when the padelectrode 205 a and the ground are not connected in the mask layer, thepotential of the select signal SEL can be set to an H level. If a groundlead 9 b is placed adjacent to the lead 9 a, then the potential level ofthe select signal SEL can be brought to the L level when the padelectrode 205 a and the ground lead 9 b are electrically connected toeach other by a wire. Further, even if the mask layer is used to connectbetween the pad electrode 205 a and the ground, power consumptionincreases but the potential level of the select signal SEL can bebrought to the H level if the pad electrode 205 a is electricallyconnected to the source lead 9 a by the wire.

Various forms can be taken as the selecting methods employed in thesecond embodiment as described above. Therefore, any of theabove-described various selecting methods is applied according to theconfiguration and purposes of a product to which the semiconductordevice of the present invention is applied, thereby making it possibleto satisfy their purposes.

While the MCP types, any of which connects between the plurality of LSIchips by using the wires, have been described above by way of example,the present invention is not limited to these. The following can also beconsidered as ones for application.

For example, a plurality of LSI chips are respectively implemented overa substrate on the same plan side without being stacked on one anotherand may be interconnected with one another by printed wiring on thesubstrate. Described specifically, the pad electrodes 105 and the padelectrodes 125 of the LSI chip 103 are wire-bonded so as to berespectively electrically connected to predetermined wiring portionsprovided over a substrate on which the LSI chip 103 itself isimplemented. The pad electrodes 115 of the LSI chip 113 are similarlywire-bonded so as to be respectively electrically connected topredetermined wiring portions provided over a substrate on which the LSIchip 113 itself is implemented. Here, the pad electrodes 115 and the padelectrodes 135 are subjected to wire bonding so as to be electricallyconnected to one another via wires provided over the substrate. Further,the wires on the substrate, to which the pad electrodes 105 areconnected by wire bonding, are further electrically connected toexternal terminals like leads by wire bonding and electrically connectedto bump electrodes provided over a plane surface on the non-implementedside of LSI chips via through holes or the like.

Further, the LSI chips may respectively be placed over the front andback of a die for a lead frame or a substrate so as to be interconnectedwith each other. Described specifically, the LSI chip 103 is placed overthe surface of the substrate. Further, the pad electrodes 105 and thepad electrodes 125 of the LSI chip 103 are respectively wire-bonded soas to be electrically connected to predetermined wiring portionsprovided on the implemented surface side of the LSI chip 103 itself. TheLSI chip 113 is placed over the back of the substrate, and the padelectrodes 115 of the LSI chip 113 are respectively subjected to wirebonding so as to be electrically connected to predetermined wiringportions provided on the implemented back side of the LSI chip 113itself. The pad electrodes 115 and the pad electrodes 125 areelectrically connected to one another via the wires and through holesprovided in the substrate. The wires to which the pad electrodes 105 areconnected by wire bonding, are further electrically connected toexternal terminals like leads by wire bonding.

Further, the pad electrodes may be provided so as to interconnect theLSI chips by a bump structure. This result in such a configuration thatthe pad electrodes 105 and the pad electrodes 125 are directly connectedto one another without using the wire bonding.

In either case, the LSI chips having the pad electrodes, which show oneslike the present invention, can be applied and these plural LSI chipscan be interconnected with one another to implement a desired function.

However, as viewed from the need or the like for coping with increasesin cost and size due to the use of the substrate, a difficulty ininterconnecting between LSI chips using the front and back of a die, anda change in the placement or layout of pad electrodes to be connected tothe upper LSI chip, which are employed in the lower LSI chip withrespect to a change in the placement of pad electrodes of the upper LSIchip, it can be said that ones interconnected with each other by wirebonding as laminated structures are more suitable.

However, when it is desired to avoid to the utmost, the influence ofstress on the LSI chips each using the laminated structure due tovarious factors such as wire bonding, etc., the two LSI chips areimplemented on the substrate as described above and may more preferablybe interconnected with each other using the substrate. Therefore, themethod using the substrate is suitable for such a product as to placeemphasis on a reduction in stress, and a product having other factorscapable of sufficiently making up for a cost standpoint.

Although associated even with the influence of stress on theaforementioned LSI chips, the second embodiment has been described withthe LSI chip 203 large in size as the micon and the LSI chip 213 smallin size as the batch erasable EEPROM. However, the present invention isnot necessarily limited to these. For example, the LSI chip 203 large insize and the LSI chip 213 small in size may be set as the batch erasableEEPROM and the micon respectively.

This makes allowance even for the case where the LSI chip used as themicon is smaller in size than the LSI chip used as the batch erasableEEPROM depending on a manufacturing process applied to the laminated twoLSI chips, for example. However, when the LSI chip 203 large in size isset as the batch erasable EEPROM and the LSI chip small in size is setas the micon, the following points should be taken into consideration.

FIG. 24 is a view showing the layout of internal circuits at the timethat a batch erasable EEPROM is used as an LSI chip 913 equivalent tothe LSI chip 203.

The LSI chip 913 comprises a memory cell area 913-1 in which a memorycell unit is placed, a first peripheral circuit area 913-2 in whichperipheral circuits such as a charge pump circuit, etc. are placed, anda second peripheral circuit area 913-3 in which other peripheralcircuits are placed. At this time, the memory cell unit placed in thememory cell area 913-1 is apt to cause a change in characteristic due tothe influence of stress. FIG. 25 is a plan view showing an LSI chip 903used as a micon, which is stacked on a main surface of the LSI chip.913. FIG. 26 is a plan view showing the relationship of layout betweenthe LSI chip 903 shown in FIG. 25 and the internal circuits in the LSIchip 913. Incidentally, FIG. 25 shows a state in which leads, a resinfor encapsulation and wires are omitted therefrom.

As shown in FIG. 25, pad electrodes 915 for interfacing to each internalcircuit of the LSI chip 903 are placed over the main surface of the LSIchip 913. In FIG. 25, the pad electrodes 915 are respectively placed inline along the two sides around the outer periphery of the LSI chip 913.The LSI chip 903 is placed over the main surface of the LSI chip 913.Pad electrodes 925 for interfacing to the internal circuits of the LSIchip 913, which are to be respectively electrically connected to the padelectrodes 915, are placed in line over the main surface of the LSI chip903. The pad electrodes 925 are placed along the respective sides of theLSI chip 903, which are parallel to the sides of the LSI chip 913 alongwhich the pad electrodes 915 are placed, and which are close thereto, inconsideration of ease of a wire bonding process. Further, pad electrodes905 to be electrically connected to leas for connection to unillustratedouter portions are placed in line over the main surface of the LSI chip903. The pad electrodes 905 may be placed in a staggered arrangementwith the pad electrodes 925 along the same sides as those for theplacement of the pad electrodes 925, which lie around the outerperiphery of the LSI chip 903. Alternatively, the pad electrodes 905 maybe placed along the non-placed sides of the pad electrodes 925. If theinterval between the adjacent pad electrodes 905 is wide where the padelectrodes 905 are placed along the same sides as the placed sides ofpad electrodes 925, then the pad electrodes 925 may respectively beplaced between the pad electrodes 905, and the pad electrodes 905 andthe pad electrodes 925 may be placed in line in a row. In this case, itis hard to make a distinction between the pad electrodes 905 to beconnected to leads and the pad electrodes 925 upon wire bonding. It ishowever easy to prevent short circuits developed in wires forrespectively electrically connecting the pad electrodes 905 and theleads by wire bonding and wires for respectively electrically connectingthe pad electrodes 915 and the pad electrodes 925. It is not necessaryto increase the height of the top of each wire for electricallyconnecting the pad electrode 905 and the lead by wire bonding for thepurpose of preventing such short circuits. Therefore, the thickness ofthe resin for encapsulation can also be made thin. Incidentally, the padelectrodes 925 may be placed in consideration of wire bonding to theleads to be connected.

As shown in FIG. 26, the LSI chip 903 (whose area to be placed isindicated by a dotted line in FIG. 26) is placed so as to fully cover aportion above a memory cell area 913-1 on which a memory cell unit in anLSI chip 913 is placed.

Owing to such a layout, the following advantageous effects can bebrought about. Namely, it is understood that due to the differencebetween thermal expansion coefficients of the LSI chips 903 and 913, thedifference between thermal expansion coefficients of resins forencapsulating these LSI chip, etc., an upper portion of each memorycell, which is covered with the LSI chip 903 and an upper portionthereof which is not covered with the LSI chip 903, exist in the memorycell assuming that an area 913-2 shown in FIG. 26 is defined as a memorycell area, for example. When the LSI chips placed in laminated form insuch a condition, are sealed with a resin, stress applied to each memorycell becomes nonuniform (particularly, each memory cell at the boundarybetween the portion covered with the LSI chip 903 and the portionuncovered with the LSI chip 903 in the memory cell area) due to thedifference between the thermal expansion coefficients or the likereferred to above. As a result, this exerts an influence on thecharacteristic of the memory cell. Therefore, when another LSI chip 903is placed over the LSI chip 913 having such a memory cell area inlaminated form, the upper portion of the memory cell area 913-1 isplaced so as to be fully covered with the LSI chip 903, thereby makingit possible to solve the above problem.

FIG. 27 is a cross-sectional view of a semiconductor device wherein thetwo laminated LSI chips shown in FIG. 25 are encapsulated in resin. FIG.27 is equivalent to a cross-section taken along line A-A′ of FIG. 25.Elements of structure similar to those shown in FIG. 1 are identified bythe same reference numerals. As shown in FIG. 27, pad electrodes 915 forinterface and pad electrodes 925 are respectively electrically connectedto one another by wires 917. Further, pad electrodes 905 and leads 9 arerespectively electrically connected to one another by wires 907. It isnecessary to sufficiently increase the height of the top of each wire907 for the purpose of avoiding short circuits developed in the wires907 and 917. The semiconductor device is sealed with a resin forencapsulation 10 with a sufficient thickness to avoid the exposure ofthe wires 917 to the outside.

FIG. 28 is a view showing a modification of the layout of internalcircuits employed in an LSI chip 913. In a manner similar to FIG. 26, anarea in which an LSI chip 903 is placed, is indicated by a dotted line.In FIG. 28, a memory cell area 913-1 is set to a substantially centralarea of the LSI chip 913. The periphery of the memory cell area 913-1 isdivided into a first peripheral circuit area 913-2 and a secondperipheral circuit area 913-3 respectively. When laid out in this way,the upper portion of the memory cell area 913-1 can be fully coveredwith the LSI chip 903 if the LSI chip 903 is placed over a main surfaceof the LSI chip 913 so as to cover the substantially central area of theLSI chip 913.

FIG. 29 is a plan view showing an LSI chip 903 used as a micon, which isstacked over the main surface of the LSI chip 913 shown in FIG. 28. Byplacing the memory cell area 913-1 as shown in FIG. 28, such a layout ofpad electrodes as shown in FIG. 29 can be materialized. Namely, the padelectrodes 925 for interface can respectively be placed along theparallel two sides around the outer periphery of the LSI chip 903, andthe pad electrodes 905 for connection to leads can respectively beplaced along other parallel two sides thereof. The pad electrodes 915are provided in the neighborhood of the outer periphery of the LSI chip,on which the pad electrodes 925 are laid out.

FIGS. 30 and 31 are respectively cross-sectional views of asemiconductor device in which two laminated LSI chips shown in FIG. 31are sealed with a resin. FIG. 30 is equivalent to a cross-section takenalong line A-A′ of FIG. 29, and FIG. 31 is equivalent to a cross-sectiontaken along line B-B′ of FIG. 29, respectively.

As shown in FIG. 30, the pad electrodes 905 are electrically connectedto their corresponding leads 9 by wires 907. As. shown in FIG. 31, thepad electrodes 915 are electrically connected to their corresponding padelectrodes 925 by wires 917.

Thus, since the pad electrodes 905 and the pad electrodes 925 can beplaced along the different sides on the outer periphery of the LSI chip903 respectively as is understood from FIGS. 28 through 31, such aproblem as to short-circuit the wires 907 and 917 does not arise. Sinceit is not necessary to increase the height of the top of each wire 907for purposes of the prevention of such short circuits, the thickness ofa resin for encapsulation in FIG. 30 can also be made thin as comparedwith FIG. 27. Since the pad electrodes 905 and the pad electrodes 925are placed along the different sides respectively, miswire bonding canalso be reduced.

The LSI chip 913 has been described as the batch erasable EEPROM above.If one equipped with a memory cell or circuit which develops a stressproblem similar to the batch erasable EEPROM, is used, then the LSI chip913 is not limited to the batch erasable EEPROM and the methods shown inFIGS. 24 through 31 can be applied. Further, the LSI chip 903 might notbe limited to the micon. In an MCP using. LSI chips different in size, asufficient effect can be brought about even if the layout of the LSIchips in the MCP having allowed for such stress is applied to theconventional MCP shown in FIG. 17.

In the present invention as described above, for example, either one oftwo LSI chips can be applied even if used as a micon or even if used asa memory. Namely, if one LSI chip is provided with the pad electrodes125 for interface and the pad electrodes 105 for connection to the leadsas in the LSI chip 103, then the LSI chip having the pad electrodes 105and the pad electrodes 205 may be laid out over the other LSI chip whenthe other LSI chip is large in size. When the other LSI chip is small insize, the LSI chip small in size may be placed over the LSI chip havingthe pad electrodes 105 and the pad electrodes 205. Owing to thedevelopment of one LSI chip in this way, ones having various sizes andfunctions can be applied as the other LSI chip. Thus, various systemLSIs can be offered or provided in a short period of time. Since it isnot necessary to redevelop one LSI chip again in this case, a reductionin cost can also be achieved.

Incidentally, the various modifications and applications described inthe present specification can be applied even to the configurationsdescribed in FIGS. 24 through 31.

The pull-down resistors and N channel MOS transistors employed in thecircuits shown in the above-described embodiments, modifications andapplications may be used as pull-up resistors and P channel MOStransistors according to the use of the potential level of the selectsignal SEL, respectively. Other signals may be used without limitationsto the reset signal RES. However, the reset signal RES is suitable asone automatically set upon the initial operation of the LSI chip.

According to the semiconductor device of the present invention asdescribed above, a system LSI can easily be implemented by asemiconductor device wherein a plurality of LSI chips are sealed with aresin.

According to the semiconductor device of the present invention as well,problems developed upon implementation of a system LSI by asemiconductor device wherein a plurality of LSI chips are sealed with aresin, can be solved. The system LSI can be implemented withoutimpairing a function set as for the system LSI even as compared with theconventional one.

While the present invention has been described with reference to theillustrative embodiments, this description is not intended to beconstrued in a limiting sense. Various modifications of the illustrativeembodiments, as well as other embodiments of the invention, will beapparent to those skilled in the art on reference to this description.It is therefore contemplated that the appended claims will cover anysuch modifications or embodiments as fall within the true scope of theinvention.

1. A semiconductor device comprising: a first semiconductor elementhaving a first surface of a quadrangle shape and a second surface of aquadrangle shape; and a second semiconductor element having a firstsurface of a quadrangle shape and a second surface of a quadrangleshape, the first semiconductor element placed above the first surface ofthe second semiconductor element so that the second surface of the firstsemiconductor element faces the first surface of the secondsemiconductor element, wherein a size of the first and second surfacesof the first semiconductor element are smaller than a size of each ofthe first and second surfaces of the second semiconductor element, andwherein a size of the first semiconductor element is smaller than acircuit element area of the second semiconductor element, and whereinthe first semiconductor element is placed against one side of the secondsemiconductor element, so that an edge of the second surface of thefirst semiconductor element is not placed above a predetermined circuitblock in the circuit element area of the second semiconductor element.2. The semiconductor device according to claim 1, whereincharacteristics of the predetermined circuit block change with stress ata rate greater than characteristics of other circuits under the edge ofthe second surface of the first semiconductor element.
 3. Thesemiconductor device according to claim 2, wherein the predeterminedcircuit block is a memory cell array.
 4. The semiconductor deviceaccording to claim 2, wherein the first semiconductor element includesfirst circuits that implement a desired function and second circuits,and the second semiconductor element includes third circuits includingthe predetermined circuit that also implement the desired function. 5.The semiconductor device according to claim 2, wherein the firstsemiconductor element has a plurality of first electrodes in the firstsurface of the first semiconductor element, and the second semiconductorelement has a plurality of second electrodes in the first surface of thesecond semiconductor element for being electrically connected toexternal connecting terminals.
 6. The semiconductor device according toclaim 5, wherein the predetermined circuit block is a memory cell array.7. The semiconductor device according to claim 5, wherein the firstsemiconductor element includes first circuits that implement a desiredfunction and second circuits, and the second semiconductor elementincludes third circuits including the predetermined circuit that alsoimplement the desired function.
 8. The semiconductor device according toclaim 5, wherein the plurality of second electrodes are electricallyconnected to the external connecting terminals by wires.
 9. Thesemiconductor device according to claim 5, further comprising aplurality of third electrodes in the first surface of the secondsemiconductor element for being electrically connected to the firstelectrodes.
 10. The semiconductor device according to claim 9, whereinthe predetermined circuit block is a memory cell array.
 11. Thesemiconductor device according to claim 10, wherein the firstsemiconductor element includes first circuits that implement a desiredfunction and second circuits, and the second semiconductor elementincludes third circuits including the predetermined circuit that alsoimplement the desired function.
 12. The semiconductor device accordingto claim 9, wherein the first semiconductor element includes firstcircuits that implement a desired function and second circuits, and thesecond semiconductor element includes third circuits including thepredetermined circuit that also implement the desired function.
 13. Thesemiconductor device according to claim 9, wherein the plurality ofthird electrodes are electrically connected to the first electrodes bywires.
 14. The semiconductor device according to claim 1, wherein thefirst semiconductor element includes first circuits that implement adesired function and second circuits, and the second semiconductorelement includes third circuits including the predetermined circuit thatalso implement the desired function.
 15. A semiconductor devicecomprising: a first semiconductor element having a first surface of aquadrangle shape and a second surface of a quadrangle shape; and asecond semiconductor element having a first surface of a quadrangleshape and a second surface of a quadrangle shape, a plurality ofrespective different circuit areas including a memory cell area aredisposed on the first surface of the second semiconductor element, thefirst semiconductor element placed above the first surface of the secondsemiconductor element so that the second surface of the firstsemiconductor element faces the first surface of the secondsemiconductor element, wherein a size of the first and second surfacesof the first semiconductor element are smaller than a size of each ofthe first and second surfaces of the second semiconductor element, andwherein a size of the first semiconductor element is smaller than acircuit element area of the second semiconductor element, and wherein anedge of the second surface of the first semiconductor element is over atleast one of the circuit areas of the second semiconductor element otherthan the memory cell area.
 16. The semiconductor device according toclaim 15, wherein the first semiconductor element has a plurality offirst electrodes in the first surface of the first semiconductorelement, and the second semiconductor element has a plurality of secondelectrodes in the first surface of the second semiconductor elementelectrically connected to external connecting terminals.
 17. Thesemiconductor device according to claim 16, further comprising aplurality of third electrodes in the first surface of the secondsemiconductor element electrically connected to the first electrodes.18. The semiconductor device according to claim 16, wherein theplurality of second electrodes are electrically connected to theexternal connecting terminals by wires.
 19. The semiconductor deviceaccording to claim 15, wherein the first semiconductor element includesfirst circuits that implement a desired function and second circuits,and the second semiconductor element includes third circuits includingthe memory cells in the memory cell area that also implement the desiredfunction.
 20. The semiconductor device according to claim 15, whereinthe circuit areas also include peripheral circuit areas in addition tothe memory cell area.